Water developable lithographic composition

Abstract

This invention relates to a radiation polymerizable composition for use in a photographic element such as a lithographic printing plate comprising in admixture (a) a binder resin having the general formula --A--B--C-- wherein a plurality of each of components A, B and C occur in ordered or random sequence in the resin and wherein A is present in said resin at about 5% to about 20% by weight and comprises groups of the formula ##STR1## B is present in said resin at about 4% to about 30% by weight and comprises groups of the formula ##STR2## and C is present in said resin at about 50% to about 91% by weight and comprises acetal groups consisting of groups of the formulae ##STR3## where R is lower alkyl or hydrogen, and wherein said group I is present in component C from about 75% to about 85%, group II is present in component C from about 3% to about 5%; and group III is present in component C from about 10% to about 22%; (b) a photoinitiator; (c) a photopolymerizable mixture of (1) a polyethoxylate diacrylate monomer; and (2) an oligomeric amine diacrylate.

We claim: 
     
       1. A radiation-polymerizable composition comprising in admixture (a) a binder resin having the general formula   --A--B--C--        wherein a plurality of each of components A, B and C occur in ordered or random sequence in the resin and wherein A is present in said resin at about 5% to about 20% by weight and comprises groups of the formula ##STR20##  B is present in said resin at about 4% to about 30% by weight and comprises groups of the formula ##STR21##  and C is present in said resin at about 50% to about 91% by weight and comprises acetal groups consisting of groups of the formulae ##STR22##  where R is lower alkyl or hydrogen, and wherein said group I is present in component C from about 75% to about 85%, group II is present in component C from about 3% to about 5%; and group III is present in component C from about 10% to about 22%;   (b) a photoinitiator; and   (c) a photopolymerizable mixture of (1) a polyethoxylate diacrylated monomer;   (2) an oligomeric amine diacrylate.     
     
     
       2. The composition of claim 1 wherein said photopolymerizable mixture further comprises a multifunctional acrylate monomer having two or more unsaturated groups, and an oligomeric urethane acrylate having one or two unsaturated groups. 
     
     
       3. The composition of claim 1 wherein said polyethoxylate diacrylated monomer has the formula ##STR23## 
     
     
       4. The composition of claim 1 wherein said oligomeric amine diacrylate has the formula ##STR24## wherein R 1  is ##STR25## where n=0-4; and R 2  is hydrogen, hydroxyl or --(CH 2 ) m  OH where m=1-4. 
     
     
       5. The composition of claim 2 wherein said multifunctional acrylate monomer is trimethylolpropane ethoxylate triacrylate. 
     
     
       6. The composition of claim 2 wherein said oligomeric urethane acrylate has the formula ##STR26## wherein ##STR27## and R 4  =R 5  =C 6  H 3  R 7  ##STR28## wherein R 7  =--CH 3  or --H. 
     
     
       7. The composition of claim 1 wherein said photoinitiator is a thioxanthone compound. 
     
     
       8. The compound of claim 7 wherein said thioxanthone compund is 2-isopropyl-9H-thioxanthen-9-one. 
     
     
       9. The composition of claim 1 wherein said photoinitiator comprises a triazine compound. 
     
     
       10. The composition of claim 9 wherein said photoinitiator comprises a bis-trichloromethyl triazine having the formula ##STR29## wherein Ar is ##STR30## and R 8 , R 9 , R 10 , and R 11  are, independently, hydrogen, chlorine, bromine, alkoxy, alkyl ketone, naphthyl or anthracyl. 
     
     
       11. The composition of claim 10 wherein said photoinitiator is 2-stilbenyl-4,6-di(trichloromethyl)triazine. 
     
     
       12. The composition of claim 1 wherein R is ethyl. 
     
     
       13. The composition of claim 1 wherein R is methyl. 
     
     
       14. The composition of claim 1 wherein said binder resin is present at from about 8% to about 18% by weight. 
     
     
       15. The composition of claim 14 wherein said binder resin is present at from about 10% to about 12% by weight. 
     
     
       16. The composition of claim 1 wherein said diacrylate monomer is present at from about 4% to about 14% by weight. 
     
     
       17. The composition of claim 16 wherein said diacylate monomer is present at from about 5% to about 7% by weight. 
     
     
       18. The composition of claim 1 wherein said oligomeric amine diacrylate is present at from about 1.5% to about 14% by weight. 
     
     
       19. The composition of claim 18 wherein said oligomeric amine diacrylate is present at from about 5% to about 7% by weight. 
     
     
       20. The composition of claim 2 wherein said multifunctional acrylate monomer is present at up to about 12% by weight. 
     
     
       21. The composition of claim 20 wherein said multifunctional acrylate monomer is present at from about 2% to about 4% by weight. 
     
     
       22. The composition of claim 2 wherein said oligomeric urethane acrylate is present at up to about 12% by weight. 
     
     
       23. The composition of claim 22 wherein said oligomeric urethane acrylate is present at from about 2% to about 4% by weight. 
     
     
       24. The composition of claim 7 wherein said triazine compound is present at from about 0.2% to about 1.0% by weight. 
     
     
       25. The composition of claim 24 wherein said triazine compound is present at from about 0.5% to about 0.7% by weight.